Automatic lathe and method of controlling same

ABSTRACT

A turret ( 11 ) is clamped to a tool rest main body ( 10 ) by a pair of coupling members ( 27 ). During indexing rotation for selecting a tool, the tool rest main body ( 10 ) and the turret ( 11 ) are moved relatively in a Z-axis direction, and the pair of coupling members ( 27 ) are unclamped. At this time, the tool rest main body ( 10 ) is moved in the Z-axis direction relative to a lathe main body ( 100 ) in synchronism with the relative movement in the Z-axis direction between the tool rest main body ( 10 ) and the turret ( 11 ). This movement of the tool rest main body ( 10 ) is adjusted in direction and moving distance so that the relative movement between the turret ( 11 ) and a spindle table ( 1 ) is eliminated. As a result of this movement control, the turret ( 11 ) and the tool fitted to the former do not have relative displacement to the spindle table ( 1 ) and to a work, so that the danger of mutual interference among these constituent elements and the work can be eliminated.

TECHNICAL FIELD

The present invention relates to an automatic lathe provided with aturret device that can be fitted with a plurality of tools and selecttools optionally through indexing rotations.

BACKGROUND TECHNOLOGY

There has recently been an increasing demand for automatic lathesprovided with a turret device that can be fitted with a plurality oftools so as to cope with a need for adopting to a large variety andsmall quantity manufacturing system while effecting automation as wellas speedup of machining operation.

The turret device is structured such that a turret mounted on a toolrest main body is capable of executing indexing rotations so as topresent any of normally 5 to 12 indexing positions optionally. Toolmounting portions are formed on a peripheral face or an outer end faceof the turret, and various tools such as a turning tool, a drill, and soforth can be mounted on the respective tool mounting portions, enablingautomatic selection of suitable tools according to the content of amachining operation through indexing rotations of the turret.

A pair of coupling members capable of engaging with each other anddisengaging from each other (clamping/unclamping) are provided betweenthe tool rest main body and the turret, and the turret can be renderedfreely rotatable or fixedly held for positioning in a given indexingposition by engaging the pair of the coupling members with each other ordisengaging the same from each other.

For the coupling members described above, coupling members in the formof crown gears of a curvic coupling or the like for being meshed witheach other are generally adopted.

With this type of the coupling members, engagement and disengagementthereof are normally effected by moving a coupling member disposed onthe turret side in the axial direction relative to a coupling memberdisposed on the side of the tool rest main body. More specifically, foreffecting the indexing rotation of the turret, engagement between therespective coupling members is released by moving the turret in theaxial direction relative to the tool rest main body, and while therespective coupling members are kept in this state, the indexingrotation of the turret is executed.

The indexing rotation of the turret is executed subsequently tocompletion of a machining operation with the use of a certain tool.Accordingly, a workpiece and a main spindle table for supporting theworkpiece are present in the vicinity of the turret at the time of theindexing rotation.

Hence, if the indexing rotation of the turret is executed with theturret kept in a position where it is present upon completion of themachining operation, this involves a risk of the turret and a toolfitted to the turret coming to interfere with the main spindle table andthe workpiece as a result of a movement of the turret in the axialdirection.

Accordingly, it has been conventionally necessary to carry outprogramming for a machining operation such that the indexing rotation ofthe turret is executed after the turret device is moved to a positionwhere such interference can be avoided.

Such programming for a machining operation needs to be carried out by auser himself according to the content of the machining operation. Amachining program to be inputted in an automatic lathe is generallydeveloped by a user while referring to a design drawing of a product.

However, the movement of the turret in the axial direction accompanyingthe indexing rotation thereof can not be known from the design drawingof the product, because the movement is a motion depending on astructure of the automatic lathe. Accordingly, it has been troublesomefor the user to develop a machining program always taking into account adistance of the movement. Furthermore, there has been a risk of theuser's making a mistake of developing a machining program without takinginto account the movement of the turret in the axial directionassociated with the indexing rotation. In case of such a mistake beingmade, there is a possibility of the turret and tools coming to interferewith the main spindle table and the workpiece, thereby destroying thelatter.

In addition, if the turret device is caused to make an evacuating motionevery time when the indexing rotation of the turret is executed, thiswill result in a longer machining time by at least the length of timetaken for making the motion.

In the light of such circumstances as described, the present inventionhas been developed, and an object of the invention is to prevent theturret and a tool fitted thereto from interfering with the main spindletable and the work, and to shorten machining time by eliminating themovement of the turret relative to a lathe main body on which the mainspindle table is mounted during the indexing rotations of the turretwhile simplifying programming by the user for a machining operation.

DISCLOSURE OF THE INVENTION

To this above described end, the automatic lathe according to theinvention comprises the following:

(1) a lathe main body with a main spindle table mounted thereon;

(2) a tool rest main body freely movable on the lathe main body at leastin a z-axis direction parallel with a main spindle axis;

(3) a turret mounted on the tool rest main body, and capable ofrelatively moving in the z-axis direction against the tool rest mainbody and indexing around a rotary center parallel to the z-axis;

(4) a pair of coupling members installed on the tool rest main body andthe turret, respectively, and capable of engaging with and disengagingfrom each other as a result of a relative movement in the z-axisdirection taking place between the tool rest main body and the turret;and

(5) control means for eliminating a relative movement between the turretand the main spindle table by moving the tool rest main body in thez-axis direction relative to the lathe main body, in synchronizationwith the relative movement in the z-axis direction taking place betweenthe tool rest main body and the turret.

In this connection, the main spindle table is a constituent element forholding and rotating the workpiece. The axis of rotation for theworkpiece supported by the main spindle table is called a main spindleaxis, and the tool rest main body is structured so as to be freelymovable at least in the z-axis direction parallel with the main spindleaxis.

A plurality of tools are optionally mountable on the turret, and toolsas required can be automatically selected by the indexing rotation ofthe turret. And through a relative movement between the main spindletable and the tool rest main body, the workpiece supported by the mainspindle table is machined into a required shape.

The turret is clamped to the tool rest main body by the pair of thecoupling members. During the indexing rotation for selecting a tool, thepair of coupling members are unclamped by relatively moving the toolrest main body against the turret in the z-axis direction, so that theturret is rendered freely indexable.

Hereupon, the control means causes the tool rest main body to move inthe z-axis direction relative to the lathe main body, in synchronizationwith the relative movement in the z-axis direction taking place betweenthe tool rest main body and the turret. The movement of the tool restmain body is adjusted in respect of direction and moving distance suchthat the relative movement between the turret and the main spindle tableis eliminated.

As a result of such control of movement as described, there will occurno relative displacement of the turret and a tool fitted thereto againstthe main spindle table and a work, thereby eliminating a risk of mutualinterference taking place among these constituent elements including thework.

At the time of the indexing rotation of the turret, the relativedisplacement between the workpiece supported by the main spindle tableand the tool fitted to the turret is thus eliminated, so programming formachining may be carried out by a user on the basis of a position of theworkpiece relative to the tool at the time of completion of a machiningoperation. Accordingly, there will be no need to take into account therelative displacement between the workpiece and the turret, accompanyingthe indexing rotation of the turret, as with the conventional case,thereby facilitating operation.

Further, since there will be no need of evacuating the turret deviceprior to the indexing rotation of the turret, machining time can beshortened by at least a length of time saved due to omission of such amotion.

Also, if a main spindle table is movable on a lathe main body at leastin a z-axis direction parallel with a main spindle axis, the inventionmay have such a configuration that control means is able to eliminate arelative movement between a turret and the main spindle table by movingthe main spindle table in the z-axis direction relative to the lathemain body, in synchronization with a movement of the turret in thez-axis direction.

The movement of the main spindle table in this case is adjusted inrespect of direction and moving distance in such a way as to eliminatethe relative movement between the turret and the main spindle table.

The present invention may also be applicable to an automatic lathecomprising a tool rest main body that is freely movable on a lathe mainbody at least in an x-axis direction orthogonal to a main spindle axis,and a pair of coupling members capable of engaging with and disengagingfrom each other as a result of a relative movement in the x-axisdirection taking place between the tool rest main body and a turret.

In this case, the invention comprises control means for eliminating arelative movement between the turret and a main spindle table by movingthe tool rest main body in the x-axis direction relative to the lathemain body, in synchronization with the relative movement in the x-axisdirection taking place between the tool rest main body and the turret.

The movement of the tool rest main body in this case is adjusted inrespect of direction and moving distance in such a way as to eliminatethe relative movement between the turret and the main spindle table.

Further, the present invention can be embodied by a method ofcontrolling an automatic lathe comprising a lathe main body with a mainspindle table mounted thereon, a tool rest main body freely movable onthe lathe main body at least in a z-axis direction parallel with a mainspindle axis, a turret mounted on the tool rest main body and capable ofrelatively moving in the z-axis direction against the tool rest mainbody and indexing around a rotary center parallel to the z-axis, and apair of coupling members installed on the tool rest main body and theturret, respectively, and capable of engaging with and disengaging fromeach other as a result of a relative movement in the z-axis directiontaking place between the tool rest main body and the turret.

That is, with the method of controlling the automatic lathe according tothe invention, a relative movement between the turret and the mainspindle table is eliminated by moving the tool rest main body in thez-axis direction relative to the lathe main body, in synchronizationwith the relative movement in the z-axis direction taking place betweenthe tool rest main body and the turret.

The movement of the tool rest main body in this case is adjusted inrespect of direction and moving distance in such a way as to eliminatethe relative movement between the turret and the main spindle table.

Similarly, the present invention can also be embodied by a method ofcontrolling an automatic lathe comprising a lathe main body with a toolrest main body mounted thereon, a main spindle table movable on thelathe main body at least in a z-axis direction parallel with a mainspindle axis, a turret mounted on the tool rest main body so that theturret can freely move in the z-axis direction and freely index around arotary center parallel to the z-axis, and a pair of coupling membersinstalled on the tool rest main body and the turret, respectively, andcapable of engaging with and disengaging from each other as a result ofa movement of the turret in the z-axis direction.

That is, with this method, control is effected such that a relativemovement between the turret and the main spindle table is eliminated bymoving the main spindle table in the z-axis direction relative to thelathe main body, in synchronization with the movement of the turret inthe z-axis direction.

The movement of the main spindle table in this case as well is adjustedin respect of direction and moving distance in such a way as toeliminate the relative movement between the turret and the main spindletable.

Furthermore, the present invention can also be embodied by a method ofcontrolling an automatic lathe comprising a lathe main body with a mainspindle table mounted thereon, a tool rest main body freely movable onthe lathe main body at least in a x-axis direction orthogonal to a mainspindle axis, a turret mounted on the tool rest main body and capable ofrelatively moving in the x-axis direction against the tool rest mainbody and indexing around a predetermined rotary center, and a pair ofcoupling members installed on the tool rest main body and the turret,respectively, and capable of engaging with and disengaging from eachother as a result of a relative movement in the x-axis direction takingplace between the tool rest main body and the turret.

That is, with this method, control is effected such that a relativemovement between the turret and the main spindle table is eliminated bymoving the tool rest main body in the x-axis direction relative to thelathe main body, in synchronization with the relative movement in thex-axis direction taking place between the tool rest main body and theturret.

The movement of the main spindle table in this case as well is adjustedin respect of direction and moving distance in such a way as toeliminate the relative movement between the turret and the main spindletable.

With respective configurations described in the foregoing, there willoccur no relative displacement of the turret and a tool fitted thereto,against the main spindle table and a work, so that a risk of mutualinterference occurring among those constituent elements including thework is eliminated.

In addition, since at the time of the indexing rotation of the turret,the relative displacement between the workpiece supported by the mainspindle table and the tool fitted to the turret is eliminated,programming for machining may be carried out by a user on the basis of aposition of the workpiece relative to the tool upon completion of amachining operation. Accordingly, there will be no need of taking intoaccount the relative displacement between the workpiece and the turret,accompanying the indexing rotation of the turret, as with theconventional case, thereby facilitating operation.

Furthermore, since there will be no need of evacuating the turret deviceprior to the indexing rotation of the turret, machining time can beshortened by at least a length of time saved due to omission of such amotion.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view showing an external configuration of an automaticlathe to which the invention is applied;

FIG. 2 is a sectional plan view showing a turret device;

FIG. 3 is an enlarged sectional plan view showing a state whereincoupling members mesh with each other while the clutch pieces disengagefrom each other;

FIG. 4 is an enlarged sectional plan view showing a state wherein thecoupling members disengage from each other while the clutch pieces meshwith each other;

FIG. 5 is a block diagram showing a control system of a tool slide and aturret device;

FIG. 6 is a flow chart showing a control operation of the tool slide andthe turret device according to the control system shown in FIG. 5;

FIG. 7A is an enlarged sectional view showing tooth profiles of thecoupling members;

FIG. 7B is also an enlarged sectional view showing the tooth profiles ofthe coupling members in an engagement state with each other;

FIG. 8 is a plan view showing an external configuration of an automaticlathe having another construction to which the invention is applied; and

FIG. 9 is a plan view showing an external configuration of an automaticlathe having still another construction to which the invention isapplied.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described in detailhereinafter with reference to the accompanying drawings.

FIG. 1 is a plan view showing an external configuration of an automaticlathe to which the present invention is applied. As shown in the figure,the automatic lathe is equipped with a main spindle table 1 and a turretdevice 2 mounted on a lathe main body 100.

The main spindle table 1 is provided with a chuck 3 for clamping aworkpiece W, and the workpiece W is clamped by the chuck 3. And the mainspindle table 1 has a function of rotating the workpiece W around a mainspindle axis 1 a by means of a main spindle motor (not shown)incorporated therein.

The turret device 2 is mounted on a tool slide 4. The tool slide 4 iscapable of moving the turret device 2 in a z-axis direction parallelwith the main spindle axis 1 a as well as in a x-axis directionorthogonal to the main spindle axis 1 a by a driving device which is notshown here. The turret device 2 is moved in the z-axis direction as wellas in the x-axis direction together with the tool slide 4, therebycutting the workpiece W.

FIG. 2 is a sectional plan view showing the turret device 2.

The turret device 2 is provided with a tool rest main body 10 mounted onthe tool slide 4 and a turret 11 rotatably installed on the tool restmain body 10.

The turret 11 is provided with a plurality of tool mounting portions 12installed with given indexing angles on the outer periphery of the frontend thereof. A cutting tool 13 such as a turning tool or the like,fitted to a tool holder 15, and a rotary tool 14 such as a drill or thelike, fitted to another tool holder 16, are mountable on the toolmounting portions 12, along with the tool holders 15, 16, respectively.

The tool holder 15 for the cutting tool 13 is fixed by inserting aprotrusion 15 a formed on the tool holder 15 into a mounting hole 12 aformed in one of the tool mounting portions 12, and the tool holder 15is then securely held by means of a fastening device (not shown) such asbolts and the like.

The tool holder 16 for the rotary tool 14 has a tool rotary shaft 17penetrating through the center of a holder body 16 a and rotatable,while a tool chuck 18 for clamping the rotary tool 14 is installed atthe tip of the tool rotary shaft 17. Further, a tool rotary gear 19 isinstalled at the base end portion of the tool rotary shaft 17.

The tool holder 16 for the rotary tool 14 is securely held by means of afastening device (not shown) such as bolts and the like by inserting theholder body 16 a into a mounting hole 12 a bored in one of the toolmounting portions 12 of the turret 11, whereupon the tool rotary gear 19installed at the base end portion of the tool rotary shaft 17 is causedto penetrate through the turret 11 so as to be projected behind thesame.

In this connection, the same as the well known configuration of a turretand mounted tools as applied to common machine tools may be adopted to aconfiguration of the tool mounting portions 12 and tools with respect tothe turret 11, other than the configuration described above.

A base end portion 11 a formed within a smaller diameter part of theturret 11 is fitted into the tool rest main body 10 in such a way as tobe freely rotatable around the rotary center O as well as linearlymovable along the rotary center O via a slide bearing 20 formed inside ahollow part 10 a of the tool rest main body 10.

The rotary center O extends in the z-direction that is parallel to themain spindle axis 1 a.

Further, inside the hollow part 10 a of the tool rest main body 10, aball screw 21 is installed coaxially with the rotary center O describedabove via rolling bearings 22. A motive transmission gear 23 is attachedto the base end portion of the ball screw 21.

Meanwhile, a coupling motor 24 comprising a servomotor is mounted on thetool rest main body 10. A driving gear (not shown) meshing with themotive transmission gear 23 described above is attached to the rotaryshaft of the coupling motor 24, so that rotary driving force of thecoupling motor 24 is transmitted to the ball screw 21 via the drivinggear and the motive transmission gear 23, thereby driving the ball screw21 in rotation.

A nut 25 is screwed into the ball screw 21, and fixedly attached to thebase end portion 11 a of the turret 11. Accordingly, rotation of theball screw 21 is accompanied by a linear movement of the nut 25 alongthe rotary center O, causing the turret 11 to move linearly along therotary center O (that is, in the z-axis direction) fixedly together withthe nut 25. Thus, a screw feed mechanism 26 for causing the turret 11 tomove linearly is made up of the ball screw 21 and the nut 25.

Also, the turret 11 is fitted with an annular gear 29 installedcoaxially with the rotary center O via needle bearings 28. The outerperipheral face of the annular gear 29 is provided with a gear formed soas to mesh with both the tool rotary gear 19 of the tool rotary shaft 17and a gear for transmitting driving force of an indexing motor 32 asdescribed later, while the inner peripheral face thereof is rotatablysupported by the needle bearings 28.

The inner ring of the needle bearings 28 is formed as a recess 30defined on the outer peripheral face of the turret 11, and is rotatablerelative to the turret 11, but prevented from moving in the directionalong the rotary center O, so the needle bearings 28 move togetherfixedly with the turret 11 in the same direction when the turret 11makes a linear movement along the rotary center O.

Meanwhile, as shown in FIGS. 3 and 4 with enlarged views, the annulargear 29 is structured such that a circumferential groove 29 a formed atthe rear end thereof is engaged with a protrusion 10 b formed on thetool rest main body 10, so that the annular gear 29 is held in a givenposition by engagement of the circumferential groove 29 a with theprotrusion 10 b.

The hollow part 10 a of the tool rest main body 10 has a portion thereoflarger in diameter on the tip end side thereof beyond a stepped part 10c, while the turret 11 also has a portion thereof larger in diameter onthe tip end side thereof beyond a stepped part 11 b. And a couplingmember 27 comprising a tool rest main body side coupling 27 a and aturret side coupling 27 b of a curvic coupling, is provided on the faceof the stepped part 10 c of the tool rest main body 10 and the steppedpart 11 b of the turret 11.

The couplings 27 a, 27 b, each having a tooth profile in a wellknowncrown-gear-like shape, function for positioning by meshing respectivetooth profiles with each other, and as shown in FIGS. 7A and 7B, thecouplings have an inclined tooth profile 27 c, formed at given pitches,respectively. And a linear movement of the turret 11 is accompanied by amovement of the turret side coupling 27 b fixedly attached to the turret11, in the direction denoted by “a” in FIG. 7A, so that the toothprofile 27 c of the tool rest main body side coupling 27 a and the toothprofile 27 c of the turret side coupling 27 b, opposite to each other,engage with or disengage from each other.

Further, the rear end edge of the annular gear 29 and the front face ofthe turret side coupling 27 b of the coupling member 27 provided on theturret 11 are provided with clutch pieces 31 b and 31 a, respectively,that are formed so as to oppose each other, thereby making up a clutchmember 31. An inclined tooth profile similar to that for the couplings27 a, 27 b is formed on the surfaces of the clutch pieces 31 a and 31 b,opposite to each other, at given pitches. These tooth profiles engagewith or disengage from each other as a result of a linear movement ofthe turret 11, along the rotary center O.

The engagement and disengagement between the clutch pieces 31 a, 31 bhave a reverse relationship to the engagement and disengagement betweenthe couplings 27 a, 27 b. That is, when the turret 11 is moved to theright along the z-axis in FIG. 2, relative to the tool rest main body10, the couplings 27 a, 27 b engage with each other while the clutchpieces 31 a, 31 b disengage from each other.

FIG. 3 is an enlarged view showing a state wherein the couplings 27 a,27 b, making up the coupling member 27, engage with each other,preventing the rotation of the turret 11, while the clutch pieces 31 a,31 b, making up the clutch member 31, disengage from each other.

In the state as shown in the figure, the turret 11 is prevented fromrotating by the couplings 27 a, 27 b engaging with each other, thusprecluding indexing rotation. When the turret 11 is moved to the leftalong the z-axis shown in FIG. 2, relative to the tool rest main body10, by the turning of the ball screw 21, the couplings 27 a, 27 bdisengage from each other and subsequently, the clutch pieces 31 a, 31 bengage with each other.

FIG. 4 is an enlarged view showing a state wherein the couplings 27 a,27 b disengage from each other while the clutch pieces 31 a, 31 b engagewith each other.

As shown in the figure, the annular gear 29 is in mesh with the toolrotary gear 19 fitted to the tool holder 16 for a rotary tool mounted onone of the tool mounting portions 12 of the turret 11.

Further, an indexing motor 32 comprising a servomotor is mounted on thetool rest main body 10, and the driving force of the indexing motor 32is transmitted to the annular gear 29 via a gear mechanism 33, therebyrotating the annular gear 29.

Accordingly, in the state shown in FIG. 3, the annular gear 29 isrotated by the indexing motor 32 via the gear mechanism 33, therebyrotating only the tool rotary shaft 17 fitted to the tool holder 16, sothat the rotary tool 14 is driven in rotation. On the other hand, in thestate shown in FIG. 4, wherein the couplings 27 a, 27 b disengage fromeach other and the clutch pieces 31 a, 31 b engage with each other, therotation of the annular gear 29 is transmitted to the coupling 27 bfixedly attached to the turret 11, so that the indexing motor 32 makesthe turret 11 to undergo indexing rotation.

The screw feed mechanism 26 described in the foregoing can be alteredsuch that the nut 25 is disposed on the driving side while the ballscrew 21 is disposed on the driven side. In this case, the ball screw 21is fixedly attached to the turret 11, and caused to move linearly by therotation of the nut 25 structured so as not to be able to move in themain spindle direction and capable of only rotation, so that the turret11 structured integrally with the ball screw 21 moves along the rotarycenter O, thus enabling the screw feed mechanism 26 to have the samefunction.

Further, in case that low friction and high precision are not requiredof the screw feed mechanism 26, an ordinary screw may be employed inplace of the ball screw 21.

In such a case, it is desirable to install means for restraining therotation of the turret 11 until immediately before the clutch pieces 31a, 31 b mesh with each other (for example, a key or splines that cancome off upon the position where engagement of the clutch pieces 31 a,31 b occur with each other).

Furthermore, for the coupling member 27 described in the foregoing, aHirth coupling and so forth with a similar configuration are applicablebesides the curvic coupling. Also, positioning means with the use of afriction coupling (brake) having a sufficient braking force or a shotpin may be adopted in place of the couplings 27 a, 27 b shown in FIGS. 2etc.

FIG. 5 is a block diagram showing a control system of the tool slide andthe turret device.

As shown in the figure, the control system of the turret device 2comprises a control part (CPU) 40, a ROM/RAM 41, a data storage part 42,an input part 43, a display part 44, a main spindle driver 45, acoupling motor driver 46, an indexing motor driver 47, a tool slidedriver 48, a tool replacement position detecting sensor 49, a couplingsensor 50, a clutch sensor 51, an indexing sensor 52, and so forth.

A control program for driving the turret device 2 is stored in theROM/RAM 41 beforehand. The control part 40 controls respectivecomponents of the tool slide 4 and the turret device 2 according to thecontrol program. The input part 43 comprises a keyboard etc., and datanecessary for controlling the respective components of the turret device2 (selection of tools, a shape and dimensions of a workpiece to bemachined, rotating speed of the main spindle, feeding speed of tools,and so forth) are inputted through the input part 43. These data can beinputted in an interactive mode by writing in numerical values ondisplay drawings shown on the display part 44.

The data entered from the input part 43 and various data necessary fordriving and controlling the turret device 2 are stored in the datastorage part 42.

The control part 40 sends out a predetermined command based on thecontrol program stored in the ROM/RAM 41, and the data for the selectionof tools (indexing rotation of the turret) and for machining, stored inthe data storage part 42.

The main spindle driver 45 drives a main spindle motor according to acommand sent out from the control part 40 to rotate the workpiececlamped by the chuck 3 of the main spindle table 1. The workpiece ismachined by the movement of the tool slide 4 in the z-axis direction andthe x-axis direction, and also by the rotation of the rotary tool 14driven by the indexing motor 32 as necessary.

The tool slide driver 48 drives the tool slide 4 in the z-axis and thex-axis directions by driving feed motors for the z-axis and the x-axisdirections, respectively, based on a command sent out from the controlpart 40.

A control system of the tool slide driver 48 functions also ascontrolling means for eliminating a relative movement between the turret11 and the main spindle table 1 in synchronization with the couplingmotor driver 46.

The coupling motor driver 46 executes engagement and disengagementbetween the couplings 27 a, 27 b for positioning and fixedly holding theturret 11 by driving the coupling motor 24 based on a command sent outfrom the control part 40 while executing engagement and disengagementbetween the clutch pieces 31 a, 31 b as well.

The indexing motor driver 47 executes the indexing rotation of theturret 11 or rotative driving of the rotary tool 14 by driving theindexing motor 32 based on a command sent out from the control part 40.In this case, the rotative driving of the rotary tool 14 is executed inmachining the workpiece while the indexing rotation of the turret 11 isexecuted in selecting a tool before or after the workpiece is machined.

The tool replacement position detecting sensor 49 detects whether or notthe turret device 2 is in a position suitable for tool replacement (thatis, a given backward position of the tool slide 4 where the turret 11can be indexed, corresponding to the origin point of tools) on the basisof the coordinates for the present position of the tool slide 4.

The coupling sensor 50 monitors the engagement and disengagement betweenthe couplings 27 a, 27 b, and detects an increase in the rotary torqueof the coupling motor 24 upon completion of engaging of the couplings 27a, 27 b with each other, sending out a coupling completion signal to thecontrol part 40. The clutch sensor 51 monitors the engagement anddisengagement between the clutch pieces 31 a, 31 b, and similarlysending out a clutch completion signal to the control part 40 when theclutch pieces 31 a, 31 b engage with each other.

Further, the indexing sensor 52 monitors a rotation angle during theindexing rotation of the turret 11, and sends out an indexing completionsignal to the control part 40 upon completion of the indexing rotationup to an angular position according to a command given by the controlpart 40.

As described above, with this embodiment of the invention, since thesesensors designated 49 to 52 are structured so as to be operative bydetecting a change in the rotation position or the rotary torque of theservomotor, sensors of a particular type need not be provided.

In the control system shown in FIG. 5, there is shown a configurationwherein a change in the rotation position or the rotary torque of theservomotor is detected by a detection sensor of the tool replacementposition detection sensor 49, the coupling sensor 50, the clutch sensor51 and the indexing sensor 52, respectively, however, an ordinary sensorfor detecting a position may evidently be adopted for these sensors.Furthermore, the three sensors other than the indexing sensor 52 may beomitted although it is desirable to keep all the sensors installed whenoperational safety of the automatic lathe is taken into consideration.

FIG. 6 is a flow chart showing a control operation for executing theindexing rotation, positioning and fixedly holding of the turret 11(rotary table), and the rotative driving of the rotary tool 14 by meansof the control system configured as described above. Since the controloperation is executed mainly by commands sent out from the control part40, the control operation will be described hereinafter mainly on thebasis of commands sent out from the control part 40.

The indexing motor 32 serves as a driving source for executing theindexing rotation of the turret 11 and the rotative driving of therotary tool 14. Since the rotating speed and the rotating direction ofthe indexing motor 32 varies depending on an object to be driventhereby, there are provided two modes in which the indexing motor 32 iscontrolled, that is, a mode for executing the indexing rotation of theturret 11 (T/I mode) and another mode for executing the rotary drivingof the rotary tool 14 (T/S mode), and control programs corresponding tothe respective modes are stored in the ROM/RAM 41.

First, when executing a step of indexing the turret 11 to select a nexttool upon completion of a cutting operation, the control part 40 startsthe indexing rotation of the turret 11 after checking up the completionof the cutting operation, and switches the control program of theindexing motor 32 to the T/I mode (S1).

Subsequently, a command for driving is sent out to the coupling motordriver 46, thereby driving the coupling motor 24 in rotation in theforward direction (S2).

In this embodiment of the invention, a rotating direction of thecoupling motor 24 for moving the nut 25 of the screw feed mechanism 26in the forward direction (leftward along the z-axis in FIG. 2) isdefined as the forward direction.

When the coupling motor 24 is rotated in the forward direction, therotative driving force of the coupling motor 24 is transmitted to theball screw 21 of the screw feed mechanism 26 via the motive transmissiongear 23 shown in FIG. 2, thereby turning the ball screw 21. As the ballscrew 21 is turned, the nut 25 is urged to make a linear movementforward (leftward along the z-axis) along the rotary center O. Since theturret 11 is fixedly attached to the nut 25, the turret 11 is also urgedto move forward (leftward along the z-axis) relative to the tool restmain body 10 together with the nut 25.

If the turret 11 moves forward (leftward along the z-axis) relative tothe tool rest main body 10 as above, the turret 11 and a tool (thecutting tool 13 in the case of FIG. 2) make a leftward movement alongthe z-axis, relative to the main spindle table 1 and the workpiece W,thereby raising the risk of interference.

Hence, the control part 40 drives the feed motor for the z-axisdirection by controlling the tool slide driver 48. Such control of thetool slide driver 48 is executed in synchronization with the linearmovement of the nut 25 (that is, the leftward movement of the turret 11along the z-axis relative to the tool rest main body 10) and in such away as to cause the tool slide 4 to move in the opposite direction (thatis, rightward along the z-axis of the turret 11) by a distance coveredby the linear movement of the nut 25 (S2).

Upon such a movement of the tool slide 4, the tool rest main body 10 ismoved together therewith, and consequently, there will occur no relativemovement of the turret 11 in relation to the main spindle table 1 andthe workpiece W, thus preventing interference among the respectivemembers described above.

As a result of a leftward relative movement along the z-axis takingplace between the turret 11 and the tool rest main body 10, thecouplings 27 a, 27 b of the coupling member 27, installed between thetool rest main body 10 and the turret 11, disengage from each other,rendering the turret 11 freely rotatable.

Hereupon, since a frictional force between the ball screw 21 and the nut25, making up the screw feed mechanism 26, is sufficiently smaller thanthat between the base end portion 11 a of the turret 11 and the slidebearing 20 of the tool rest main body 10, the turret 11 is caused tomove linearly without being rotated.

When the forward rotation of the coupling motor 24 as described in theforegoing is continued, the clutch pieces 31 a, 31 b of the clutch 31engage with each other as shown in FIG. 4. Upon completion of theengagement of the clutch pieces 31 a, 31 b with each other as describedabove, there will be a rapid increase in the rotary torque of thecoupling motor 24, thereby causing the clutch sensor 51 to output aclutch completion signal (S3).

The control part 40 has a timer function for measuring a length of timecounted from a time when the driving command driving is sent out to thecoupling motor driver 46 (S4), and if the clutch completion signal isnot inputted therein even after the elapse of a predetermined length oftime, the control part 40 decides it as abnormal state and stops themovement of the turret device 2 and displays an alarm (S5).

On the other hand, if the clutch completion signal is inputted in thecontrol part 40 within the predetermined length of time, the controlpart 40 stops the rotation of the coupling motor 24, thereby stoppingthe movement of the turret 11. At the same time, the control part 40stops the rotation of the feed motor for the z-axis, thereby stoppingthe movement of the tool slide 4 as well (S6).

Subsequently, the control part 40 sends out a driving command to theindexing motor driver 47 (S7), thereby rotating the indexing motor 32 ina rotating direction and by a rotation angle that are determined by thepresent tool fixing position and the tool fixing position to be selectednext. The rotative driving force of the indexing motor 32 is transmittedto the turret 11 via the gear mechanism 33, the annular gear 29 and theclutch pieces 31 a, 31 b. The turret 11 is caused to undergo indexingrotation by this rotative driving force up to the tool fixing positionto be selected next.

Now, upon the indexing rotation of the turret 11 by the rotative drivingforce of the indexing motor 32, the nut 25 of the screw feed mechanism26, fixedly attached to the turret 11, is rotated together with theturret 11. When a relative rotation takes place between the nut 25 andthe ball screw 21, the ball screw 21 is urged to make a relative linearmovement along the rotary center O by the relative rotation of the nut25.

However, since the ball screw 21 is restrained from making the linearmovement along the rotary center O by the rolling bearings 22, the nut25 is caused to move, resulting in a movement of the turret 11 along therotary center O.

When the turret 11 is caused to move rightward by the screw feedmechanism 26, the coupling 27 b, while in rotation, interferes with thecoupling 27 a, thereby disabling the indexing motor 32 to rotate, andwhen the turret 11 is caused to move leftward, the clutch piece 31 a inmesh with the clutch piece 31 b is strongly pressed thereto, therebydisabling the indexing motor 32 to rotate.

Hence, with this embodiment of the invention, the coupling motor 24 isdesigned to be rotated in a given rotating direction at a given ratio ofa rotating speed so as not to cause the relative rotation between thenut 25 and the ball screw 21 of the screw feed mechanism 26 insynchronization with the rotation of the indexing motor 32 for indexingthe turret 11.

The ratio of the rotating speed and the rotating direction between thecoupling motor 24 and the indexing motor 32 are respectively determinedby a ratio of a train of gears, a rotating direction of the gearsextending from the indexing motor 32 to the annular gear 29 (the turret11) and those from the coupling motor 24 to the ball screw 21, andtherefore, if a control program based on the foregoing is stored in theROM/RAM 41, this will suffice for the purpose described.

Upon completion of the indexing rotation of the turret 11 as describedabove, the indexing sensor 52 detects a rotated position of the indexingmotor 32, and outputs an indexing completion signal (S8).

Thereupon, the control part 40 measures a length of time elapsed fromthe time when the driving command is sent out to the indexing motordriver 47 (S9), and decides that the apparatus operates abnormally ifthe indexing completion signal is not inputted after the elapse of agiven length of time, thereby stopping the movement of the turret device2 and displaying an alarm (S5).

On the other hand, if the indexing completion signal is inputted withinthe given length of time, the control part 40 stops the rotation of theindexing motor 32, and sends out a driving command to the coupling motordriver 46, thereby rotating the coupling motor 24 in the reversedirection (S10).

Upon reverse rotation of the coupling motor 24, the rotative drivingforce thereof is transmitted to the ball screw 21 of the screw feedmechanism 26 via the motive transmission gear 23 shown in FIG. 2,causing the ball screw 21 to rotate in reverse direction. Following thereverse rotation of the ball screw 21, the nut 25 and the turret 11 areurged to make relative movement backward (rightward along the z-axisshown in FIG. 2) against the tool rest main body 10.

In this case, the turret 11 and a tool (the cutting tool 13 in the caseshown in FIG. 2) make a leftward movement along the z-axis, relative tothe main spindle table 1 and the workpiece W, raising also a risk ofinterference therebetween.

Accordingly, the control part 40 drives the feed motor for the z-axisdirection by controlling the tool slide driver 48. Such control of thetool slide driver 48 is executed in synchronization with the linearmovement of the nut 25 (that is, the rightward movement of the turret 11along the z-axis direction, relative to the tool rest main body 10), andin such a way as to cause the tool slide 4 to move in the oppositedirection (that is, in the leftward direction along the z-axis of theturret 11) by a distance covered by the linear movement of the nut 25(S10).

Since such a movement of the tool slide 4 is accompanied by a movementof the tool rest main body 10 made together with the tool slide 4,relative movement of the turret 11 against the main spindle table 1 andthe workpiece W can be eliminated, precluding a risk of interferencebetween the respective members described above.

As a result of the relative movement of the turret 11 in the rightwarddirection along the z-axis against the tool rest main body 10, theclutch pieces 31 a, 31 b come to disengage from each other.

When the reverse rotation of the coupling motor 24 is further continued,the couplings 27 a, 27 b come to engage with each other as shown in FIG.3. Upon completion of the engagement of the couplings 27 a, 27 b witheach other as described, a rapid increase in the rotary torque of theindexing motor 32 occurs, and a coupling completion signal is outputtedby the coupling sensor 50 (S11).

The control part 40 measures a length of time elapsed from a time when adriving command for reverse rotation is sent out to the coupling motordriver 46 (S12), and decides that the apparatus operates abnormally ifthe coupling completion signal is not inputted after the elapse of agiven length of time, thereby stopping a movement of the turret device 2and displaying an alarm (S5).

Meanwhile, if the clutch completion signal is inputted within the givenlength of time, the control part 40 stops the rotation of the couplingmotor 24, thereby stopping the movement of the turret 11. At the sametime, the control part 40 stops the rotation of the feed motor for thez-axis, thereby stopping the movement of the tool slide 4 as well (S13).

As a result, selection of a tool is completed.

Subsequently, the control part 40 switches the control mode of theindexing motor 32 to the mode for executing the rotative driving of therotary tool 14 (T/S mode) (S14) while reducing an output torque of thecoupling motor 24 (S15).

The output torque of the coupling motor 24 acts between the couplings 27a, 27 b via the screw feed mechanism 26, and is reduced to a measure oftorque just enough to maintain a condition of the couplings 27 a, 27 bbeing in mesh with each other (holding torque).

With this embodiment of the invention, wherein the couplings 27 a, 27 bmake up the curvic coupling and the linear movement of the turret 11 isexecuted by means of the screw feed mechanism 26, so the holding torquecan be rendered a sufficiently small torque.

A series of steps of operation for tool replacement are completed asdescribed above, and thereafter, cutting operation is executed.

In the control operation described hereinbefore, a step of checking upwhether or not the turret device 2 is presently positioned at the originpoint of tools (a position where the turret device 2 can be indexed,enabling replacement of tools) based on a detection signal sent out fromthe tool replacement position detecting sensor 49 may be inserted afterthe control program of the indexing motor 32 is switched to the T/I mode(that is, after the step S1).

If the turret device 2 is not positioned at the origin point of tools, acommand signal for movement to the origin point of tools is sent out tothe tool slide driver 48, thereby moving the tool slide 4 of the turretdevice 2 in the x-axis direction up to the origin point of tools.

By incorporating such an evacuating motion as described above in thecontrol program of the automatic lathe, the interference with obstaclesthat can not be avoided by the control operation shown in FIG. 6 can beautomatically avoided. For example, in case that the control program isswitched to the T/I mode while a tool is in contact with the workpiece,such an evasive motion can become effective.

Thus, after checking that the turret device 2 is positioned at theorigin point of tools, a driving command is issued to the coupling motordriver 46, thereby driving the coupling motor 24 in rotation in theforward direction.

Further, since the evacuating motion in the x-axis direction asdescribed above is a control motion of the feed motor for the x-axisdirection as shown in FIG. 5 while the movement of the tool slide 4 insynchronization with the rotation of the coupling motor 24 is a controlmotion of the feed motor for the z-axis direction as shown in FIG. 5,these control motions can be executed simultaneously.

Furthermore, it is possible to provide a user with such a way that theevacuating motion in the x-axis direction can be omitted, and if acommand giving a directive to that effect is incorporated in themachining program, the evacuating motion in the x-axis direction can bedispensed with.

The embodiments of the invention, described in the foregoing, has shownthe configuration wherein the tool slide 4 shown in FIG. 1 is moved inthe z-axis direction and the x-axis direction to execute cuttingoperation, however, a configuration as shown in FIG. 8 may be adoptedsuch that the main spindle table 1 is moved in the z-axis direction onthe lathe main body 100 instead of the tool slide 4 being moved in thez-axis direction.

With such a configuration, the main spindle table 1 is moved in thez-axis direction by a driving force of a main spindle table feed motor60, thereby feeding the workpiece W in the direction of the main spindleaxis. The main spindle table feed motor 60 is controlled by a mainspindle table feed driver 61. The main spindle table feed motor driver61 controls the main spindle table feed motor 60 in accordance with adirective from the control part 40 (refer to FIG. 5).

A control system for the main spindle table feed motor 60 also functionsas control means for eliminating a relative movement between the turret11 and the main spindle table 1 in synchronization with the couplingmotor driver 46.

More specifically, when the coupling member 27 is engaged or disengagedby movement of the turret 11 in the z-axis direction relative to thetool rest main body 10, prior to the indexing rotation of the turret 11,the main spindle table 1 is caused to move in the direction opposite tothe turret 11 along the z-axis for the same distance as that for themovement of the turret 11 in synchronization with the movement of theturret 11.

Such a movement of the main spindle table 1 eliminates a relativemovement of the turret 11 against the main spindle table 1 and theworkpiece W, thereby preventing interference between the respectivemembers described.

Further, the invention is applicable to an automatic lathe having aconfiguration as shown in FIG. 9 such that the rotary center O of theball screw 21 extends in a x-axis direction orthogonal to the mainspindle axis.

With this configuration, the turret 11 makes a relative movement in thex-axis direction against the tool rest main body 10 for engaging ordisengaging the coupling member 27. Hence, in synchronization with themovement of the turret 11, the tool slide 4 is caused to move in thedirection opposite to the turret 11 along the x-axis for the samedistance as that for the movement of the turret 11, whereupon the toolrest main body 10 moves together with the tool slide 4.

This movement of the tool rest main body 10 eliminates a relativemovement of the turret 11 against the main spindle table 1 and theworkpiece W, thereby preventing interference between the respectivemembers described.

INDUSTRIAL APPLICABILITY

By applying the present invention to an automatic lathe structured suchthat a turret makes a relative movement against a tool rest main body toengage or disengage a coupling member for indexing rotation of theturret, a relative movement of the turret against a main spindle tableand a workpiece can be eliminated during the indexing rotation of theturret. As a result, interference of the turret and tools with the mainspindle table and the workpiece can be prevented and machining time canbe shortened while simplifying programming by a user for machining.

What is claimed is:
 1. An automatic lathe comprising: a lathe main bodywith a main spindle table mounted thereon; a tool rest main body freelymovable on the lathe main body at least in a z-axis direction parallelwith a main spindle axis; a turret mounted on the tool rest main body,and capable of relatively moving in the z-axis direction against thetool rest main body and indexing around a rotary center parallel to thez-axis; a pair of coupling members installed on the tool rest main bodyand the turret, respectively, and capable of engaging with anddisengaging from each other as a result of a relative movement in thez-axis direction taking place between the tool rest main body and theturret; and control means for eliminating a relative movement betweenthe turret and the main spindle table by moving the tool rest main bodyin the z-axis direction relative to the lathe main body, insynchronization with the relative movement in the z-axis directiontaking place between the tool rest main body and the turret.
 2. Anautomatic lathe comprising: a lathe main body with a tool rest main bodymounted thereon; a main spindle table movable on the lathe main body atleast in a z-axis direction parallel with a main spindle axis; a turretmounted on the tool rest main body so as to be freely movable in thez-axis direction and freely indexable around a rotary center parallel tothe z-axisrotary center; a pair of coupling members installed on thetool rest main body and the turret, respectively, and capable ofengaging with and disengaging from each other as a result of a movementof the turret in the z-axis direction; and control means for eliminatinga relative movement between the turret and the main spindle table bymoving the main spindle table in the z-axis direction relative to thelathe main body, in synchronization with the movement of the turret inthe z-axis direction.
 3. An automatic lathe comprising: a lathe mainbody with a main spindle table mounted thereon; a tool rest main bodyfreely movable on the lathe main body at least in an x-axis directionorthogonal to a main spindle axis; a turret mounted on the tool restmain body, and capable of relatively moving in the x-axis directionagainst the tool rest main body and indexing around a rotary centerparallel to the z-axis; a pair of coupling members installed on the toolrest main body and the turret, respectively, and capable of engagingwith and disengaging from each other as a result of a relative movementin the x-axis direction taking place between the tool rest main body andthe turret; and control means for eliminating a relative movementbetween the turret and the main spindle table by moving the tool restmain body in the x-axis direction relative to the lathe main body, insynchronization with the relative movement in the x-axis directiontaking place between the tool rest main body and the turret.
 4. A methodof controlling an automatic lathe comprising a lathe main body with amain spindle table mounted thereon, a tool rest main body freely movableon the lathe main body at least in a z-axis direction parallel with amain spindle axis, a turret mounted on the tool rest main body andcapable of relatively moving in the z-axis direction against the toolrest main body and indexing around a rotary center parallel to thez-axis, and a pair of coupling members installed on the tool rest mainbody and the turret, respectively, and capable of engaging with anddisengaging from each other as a result of a relative movement in thez-axis direction taking place between the tool rest main body and theturret; said method characterized in that a relative movement betweenthe turret and the main spindle table is eliminated by moving the toolrest main body in the z-axis direction, relative to the lathe main body,in synchronization with the relative movement in the z-axis directiontaking place between the tool rest main body and the turret.
 5. A methodof controlling an automatic lathe comprising a lathe main body with atool rest main body mounted thereon, a main spindle table movable on thelathe main body at least in a z-axis direction parallel with a mainspindle axis, a turret mounted on the tool rest main body so as to befreely movable in the z-axis direction and freely indexable around arotary center parallel to the Z-axis, and a pair of coupling membersinstalled on the tool rest main body and the turret, respectively, andcapable of engaging with and disengaging from each other as a result ofa movement of the turret in the z-axis direction; said methodcharacterized in that a relative movement between the turret and themain spindle table is eliminated by moving the main spindle table in thez-axis direction, relative to the lathe main body, in synchronizationwith the movement of the turret in the z-axis direction.
 6. A method ofcontrolling an automatic lathe comprising a lathe main body with a mainspindle table mounted thereon, a tool rest main body freely movable onthe lathe main body at least in an x-axis direction orthogonal to a mainspindle axis, a turret mounted on the tool rest main body and capable ofrelatively moving in the x-axis direction against the tool rest mainbody and indexing around a rotary center parallel to the Z-axis, and apair of coupling members installed on the tool rest main body and theturret, respectively, and capable of engaging with and disengaging fromeach other as a result of a relative movement in the x-axis directiontaking place between the tool rest main body and the turret; said methodcharacterized in that a relative movement between the turret and themain spindle table is eliminated by moving the tool rest main body inthe x-axis direction relative to the lathe main body, in synchronizationwith the relative movement in the x-axis direction taking place betweenthe tool rest main body and the turret.